How do I clean cement stepping stones without a pressure washer?

Here are several ideas, some of them have DIY cleaners that might help too.

https://www.youtube.com/results?search_query=clean+cement+without+pressure+washer

There is a no scrub product - wet & forget outdoor - that removes the gunk over time. Watch this video. You can just spray it on with a spray bottle and let the rain and wind clean it over time. I bought it at Lowe's but QVC & walmart.como carries it as well. https://www.qvc.com/Wet-%26-Forget-Mold%2C-Mildew%2C-Moss-%26-Algae-Stain-Remover-Concentrate.product.V33711.html?sc=SRCH

If you have a sprayer, you can mix bleach and Jomax together and spray them down and scrub with a brush to clean.

Leave them in the ground or pull them up and work on a table. The caustic, dangerous way is to pour hydrochloride (hydrochloric acid) on the cement stones. Wear thick gloves and scrub them with a stiff scrubbing brush. Then rinse with water. The safer way is to cover the blocks with baking soda, pour any type vinegar on top, and let the foam work awhile (no more bubbles). Scrub with a stiff brush, and repeat if you need to. If you do repeat, in a mixing bowl add a cup of baking soda, a cup of vinegar, and a good squirt of Dawn. Mix with a wooden spoon, then dip the stiff scrubbing brush into the mixture and scrub each block hard. When (or if) the blocks are clean, Just paint them with Rustoleum red, and seal with Rustoleum Sealer for Outdoors. And keep the hostas trimmed! Best wishes, ☺️

hose and scrub brush .i use oxy clean powder 2 scoops to a gallon pail. scrub the pavers.

We use this product. You spray it on and let it sit. And, overtime it get rid of the mold and algae: Wet and Forget Moss Mold Mildew & Algae Stain Remover

I've had really good luck with Simple Green and a brush, rinsing with water. Whatever you use, especially if you use something with chemicals, please wear safety gear. Especially so that nothing splashes into your eyes.